Background prior art relating to touch sensing systems employing a plane of light can be found in U.S. Pat. No. 6,281,878 (Montellese), and in various later patents of Lumio/VKB Inc, such as U.S. Pat. No. 7,305,368, as well as in similar patents held by Canesta Inc, for example U.S. Pat. No. 6,710,770. Broadly speaking these systems project a fan-shaped plane of infrared (IR) light just above a displayed image and use a camera to detect the light scattered from this plane by a finger or other object reaching through to approach or touch the displayed image.
Further background prior art can be found in: WO01/93006; U.S. Pat. Nos. 6,650,318; 7,305,368; 7,084,857; 7,268,692; 7,417,681; 7,242,388 (US2007/222760); US2007/019103; WO01/93006; WO01/93182; WO2008/038275; US2006/187199; U.S. Pat. Nos. 6,614,422; 6,710,770 (US2002/021287); U.S. Pat. Nos. 7,593,593; 7,599,561; 7,519,223; 7,394,459; 6,611,921; D595785; 6,690,357; 6,377,238; 5,767,842; WO2006/108443; WO2008/146098; U.S. Pat. No. 6,367,933 (WO00/21282); WO02/101443; U.S. Pat. Nos. 6,491,400; 7,379,619; US2004/0095315; U.S. Pat. Nos. 6,281,878; 6,031,519; GB2,343,023A; U.S. Pat. No. 4,384,201; DE 41 21 180A; and US2006/244720.
We have previously described techniques for improved touch sensitive holographic displays, in particular in our earlier patent applications: WO2010/073024; WO2010/073045; and WO2010/073047. The inventors have continued to develop and advance touch sensing techniques relating to these systems.